Tryptophan Fluorescence

When studying biological reactions using microplate readers, a signal is needed for detection to determine what is going on in each well.

Dr EJ Dell Dr EJ Dell (10)

Microplate readers cannot just “see” DNA, proteins, or cells and usually a fluorescent or luminescent tag is necessary to illuminate the biological activity. Nature however has provided researchers with such a protein tag, that is the amino acid tryptophan. Under certain conditions tryptophan can fluorescence and be quantified. The Application Notes listed below show how several different laboratories have taken advantage of this fluorescent property of tryptophan to study the activation of heterotrimeric G proteins as well as the binding of antibodies.


  1. Using intrinsic tryptophan fluorescence to measure heterotrimeric G-protein activation
  2. Investigation of the stereoselectivity of an anti-amino acid antibody utilizing tryptophan fluorescence



Fig. 1 A: Structural models of Gαi1 (an isoform of Gα) bound to GDP (red) and GDP · AlF4- (blue) (PDB ID: 1KJY and 2IK8, respectively). The switch regions SI, SII, and SIII are in dark red and blue. Fig. 1 B: Close-up view of intrinsically-fluorescent Trp211 located in the switch II region in inactive (yellow) and activated (orange) Gαi1.


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